Villani 1998 J Biol Chem

Villani G, Greco M, Papa S, Attardi G (1998) Low reserve of cytochrome c oxidase capacity in vivo in the respiratory chain of a variety of human cell types. J Biol Chem 273: 31829-31836.

» PMID:9822650 Open Access

Villani G, Greco M, Papa S, Attardi G (1998) J Biol Chem

Abstract: The question of whether and to what extent the in vivo cytochrome c oxidase (CIV) capacity in mammalian cells exceeds that required to support respiration is still unresolved. In the present work, to address this question, a newly developed approach for measuring the rate of COX activity, either as an isolated step or as a respiratory chain-integrated step, has been applied to a variety of human cell types, including several tumor-derived semidifferentiated cell lines, as well as specialized cells removed from the organism. KCN titration assays, carried out on intact uncoupled cells, have clearly shown that the CIV capacity is in low excess (16-40%) with respect to that required to support the endogenous respiration rate. Furthermore, measurements of O₂ consumption rate supported by 0.4 mM tetramethyl-p-phenylenediamine in antimycin-inhibited uncoupled intact cells have given results that are fully consistent with those obtained in the KCN titration experiments. Similarly, KCN titration assays on digitonin-permeabilized cells have revealed a CIV capacity that is nearly limiting (7-22% excess) for ADP + glutamate/malate-dependent respiration. The present observations, therefore, substantiate the conclusion that the in vivo control of respiration by COX is much tighter than has been generally assumed on the basis of experiments carried out on isolated mitochondria. This conclusion has important implications for understanding the role of physiological or pathological factors in affecting the COX threshold. • Keywords: COX activity, KCN titration assay, TMPD, DNP, Respiration rate

Labels: MiParea: Respiration, Comparative MiP;environmental MiP 

Preparation: Intact cells, Permeabilized cells  Enzyme: Complex I, Complex IV; Cytochrome c Oxidase"Complex IV; Cytochrome c Oxidase" is not in the list (Adenine nucleotide translocase, Complex I, Complex II;succinate dehydrogenase, Complex III, Complex IV;cytochrome c oxidase, Complex V;ATP synthase, Inner mt-membrane transporter, Marker enzyme, Supercomplex, TCA cycle and matrix dehydrogenases, ...) of allowed values for the "Enzyme" property.  Regulation: Threshold;excess capacity  Coupling state: ROUTINE, ETS"ETS" is not in the list (LEAK, ROUTINE, OXPHOS, ET) of allowed values for the "Coupling states" property. 

Used cell types

• Osteosarcoma-derived cell line 143B.TK2
• SKO-007 (J3): human myeloma cell line
• A-549: human lung carcinoma cell line
• HepG2: human hepatoma cell line
• Fibroblast strain GM056059C (derived from a 14 month-old human male individual)
• Myoblast cultures (normal human individual)
• Platelets (isolated from blood of a rabbit)